Lateral buckling critical force for submarine pipe-in-pipe pipelines

The lateral buckling critical force of a submarine pipe-in-pipe pipeline with symmetrical initial imperfection on soft foundation is determined. The effects of initial imperfection shapes, out-of-straightness, soil parameters as well as lateral nonlinear pipe-soil interaction, and structure parameters (stiffness ratio of inner pipe to outer pipe and clearance between inner and outer pipes) are discussed. A simple formula considering the above factors is proposed to determine the lateral buckling critical force of submarine pipe-in-pipe pipelines based on dimensional analysis and numerical results. The accuracy of the presented formula is shown by a case study.